The present invention relates to vehicle braking systems and more particularly to a brake servomotor assembly mounted on a stationary part of a vehicle.
Conventionally (see for example the document US-A-3,358,449), a brake servomotor is mounted on the stationary wall of a vehicle separating the engine compartment from the passenger compartment, by means of mounting bolts introduced from the engine side of the vehicle into corresponding orifices formed in the stationary wall, after which a nut is screwed onto the threaded end of each bolt projecting on the other side of the stationary wall, i.e. inside the passenger compartment.
The problems arising from the compact nature and dimensions of modern vehicles make it increasingly difficult to gain access to the rear side of the stationary wall, which is generally set far back underneath the dashboard in the vicinity of the central console of the latter and the pedal fittings, such that mounting the nut on the bolt is a long and difficult operation for the operator, which could result in cross-threading of the nut and/or the bolt and therefore could lead to an imperfect or even defective assembly.
In order to obviate these drawbacks, it was also proposed, in the document EP-A-0,260,170, that the orifice in the stationary wall of the vehicle should have an elongated configuration, typically substantially in the form of an arc of a circle, with a first end zone having an enlarged cross-section, through which the nut previously mounted on the threaded end of the bolt can pass, and joined to a second end zone of the orifice with a cross-section corresponding to that of the bolt.
With such an arrangement, the nut may be easily screwed onto the bolt in advance, before mounting in position, after which the bolt, with the pre-mounted nut, is engaged through the first end zone of the orifice, the servomotor then being manually made to perform a suitable movement, typically a rotation about its axis, so as to bring the bolt into the second end zone of the orifice, the nut then being screwed down on the latter by means of a suitable screw- or bolt-tightening device.
Although, according to this document, this overcomes the problems of mounting the nut, in situ, onto the bolt in the case where there is limited access to the servomotor mounting zone inside the passenger compartment, mounting of the servomotor still requires operations which are not only manual, but also must be performed inside the passenger compartment. A large number of the abovementioned drawbacks therefore still exist.
It was also proposed, in the document EP-A-0,148,670, to fix onto the apron of a motor vehicle separating the engine compartment from the passenger compartment a pedal support also used as a support for a pneumatic brake booster. For this purpose, the support has a cylindrical part passing through the apron and limited by an internal flange, which defines a circular orifice. This flange has formed on it recesses separated by bearing surfaces intended to cooperate with the same number of lugs projecting radially outside a ring fixed to the booster by pins. The booster is mounted on the support by axially engaging lugs of the ring into corresponding recesses in the flange, and then by rotating the booster so as to bring the lugs into engagement with the bearing surfaces. A sealing ring ensures that the engine compartment and the passenger compartment are sealed with respect to each other.
Although this document overcomes various drawbacks mentioned above, some of them still exist. In fact, the servomotor is fixed onto the support by means of a ring fixed onto its rear wall. Since the servomotor is subjected to considerable forces exerted by the brake pedal, it is necessary to arrange inside the servomotor, in order to fix the pins holding the ring, corresponding reinforcements so as to prevent the plate forming the rear wall being pulled off when the brake pedal is operated. This therefore results in a proportional increase in the weight of the servomotor.
Moreover, the servomotor is held in place, by means of mutual engagement of the lugs of the ring and the bearing surfaces of the support flange, only over limited surface zones. Consequently, the force exerted in the region of these surfaces will be considerable and will therefore increase the dimensions of the internal reinforcement.
Furthermore, when the servomotor is axially engaged into the circular orifice defined by the support flange, a considerable amount of play exists between the male and female parts such that exact positioning can only be achieved through trial and error, thereby excluding the possibility of automating installation of the servomotor using a programmed automation such as an assembly robot.